Though pinworms (also referred to as seat worm or threadworm) can affect anybody, they are most common in school-aged kids. In fact pinworms are one of the most frequently occurring round worm infections in the United States. They are caused by tiny parasitic eggs which infect the intestine.
The eggs enter the digestive system and hatching takes place in the small intestine. These worms then travel to the large intestine where they live and grow. After a month or two, adult female pinworms travel to the rectal area where they lay more eggs.
These female worms tend to move around the rectal area (this is more so at night) looking for a place to lay the eggs. It is possible that these worms get out of the rectal area and spread to the vagina at night when the patient is sleeping. This pinworm infection can also cause vaginal discharge.
Possibly the worms found during menstruation, are these pinworms which have travelled from the anus to the vagina. Pinworms may be little less than an inch long and look like thin yellowish white threads with the naked eye. Of course they may not look white or yellow if they are soaked in menstrual blood. Sometimes, they can also be found in the stool.
Pinworms are contagious and spread quickly from one person to the other via contact through contaminated food, bedding items and other household items like towels, toys, bathroom fixtures etc. Hence it is important to maintain utmost hygiene.
Another possible reason for noticing worms in menstrual blood may be that women have misjudged a mucus thread in the blood as a worm. Some women experience severe menstrual cramping and pass lumps of clotted blood during menstruation. Possibly these blood clots were misinterpreted as worms, other than this worms effect on period in women is nil.
Nevertheless it is very important to consult a doctor. The above causes are just possible explanations and it is not advisable to self-diagnose or self-medicate. The doctor may order a tape test to confirm the presence of worms.
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answered by A S